# NTSB CHI91DTK04: Boland/Poe Tsunami, Pierre, SD, September 25, 1991

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Final report
- Date: September 25, 1991, 13:30 local (18:30 UTC)
- Place: Pierre, SD
- Coordinates: 44.370147, -100.319869 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.3701&lon=-100.3199&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed, report March 31, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 14881
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI91DTK04
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14881/pdf
- Page: https://openairdocs.org/ntsb/CHI91DTK04

## Probable cause

A BENDING OVERLOAD FAILURE OF THE WING FLAP CONTROL RODS AND REMEDIAL ACTION BY THE PILOT WAS NOT POSSIBLE.  FACTORS IN THE ACCIDENT ARE THE INADEQUATE DESIGN OF THE WING FLAP SYSTEM BY THE PILOT/OPERATOR MANUFACTURER AND HIS LACK OF TOTAL EXPERIENCE IN TYPE OF AIRCRAFT.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, approach - vfr pattern - final approach
  - flt control syst,wing flap control cable/rod - overload (cause)
  - acft/equip,inadequate design, manufacturer (contributing factor)
- Loss of control - in flight, approach - vfr pattern - final approach
  - remedial action - not possible, pilot in command (cause)
  - lack of total experience in type of aircraft, pilot in command (contributing factor)
- In flight collision with terrain/water, descent - uncontrolled
  - terrain condition - ground

## Analysis

THE ACCIDENT AIRPLANE WAS OBSERVED TO SUDDENLY ROLL INVERTED DURING FINAL APPROACH AND DESCEND INTO THE GROUND. INVESTIGATION OF THE WRECKAGE SHOWED A BENDING OVERLOAD FAILURE OF THE EXTERNAL THREADED STEM TYPE ROD END BEARING ATTACHED TO THE PISTON OF EACH WING FLAP HYDRAULIC ACTUATOR.  THE EXPERIMENTAL RACING AIRPLANE WAS ORIGINALLY BUILT AND FLOWN WITHOUT WING FLAPS.  THE WING FLAPS WERE ADDED BY THE PILOT/OPERATOR AT A LATER DATE.

## Aircraft

- Registration: NX39JR (not matched to a registry record)
- Reported make and model: BOLAND/POE TSUNAMI
- Category: Airplane, amateur-built
- Serial number: 001
- Airframe hours: 200
- Engines: Rolls-Royce V-1650-7 3000 horsepower reciprocating
- Damage: Destroyed
- Flight: Personal, Part 91
- Operator: John Richard Sandberg
- Registered owner: John Richard Sandberg
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, January 2, 2000
- Departed: CPR, CASPER, WY
- Airport: PIR, Pierre Municipal

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 59; private; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, unknown; seat: center; toxicology performed; flight hours: 9,975 total, 20 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 310° at 20 knots, gusting 28
- Visibility: 45 statute miles
- Lowest ceiling: none
- Temperature: 68 °F, dew point 28 °F
- Altimeter: 30.00 inHg
- Observed at: PIR, 1 nm away

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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